This application relates to an improved process for the production of S-tricyclohexyltin-O,O-diisopropyl dithiophosphate. This compound is disclosed in British Patent No. 1,349,916 as being a useful miticide and insecticide.
As disclosed in Example 1 of the British patent this compound was prepared by mixing tricyclohexyltin chloride with potassium diisopropyl dithiophosphate in acetone. Similar techniques were used in processes disclosed in U.S. Pat. Nos. 2,786,812, 3,358,006 and 3,542,825 and the article by Kubo et al., Agricultural and Biological Chemistry (Japan, 29, 43-55 (1965). The acetone and other similar solvents such as methyl ethyl ketone and lower aliphatic alcohols such as methanol and ethanol, were used in order to obtain a homogeneous reaction medium.
Potassium diisopropyl dithiophosphate is a relatively expensive reagent, whether it is first made and then isolated (similarly to the processes described in U.S. Pat. No. 3,358,006, for example), or purchased from a commercial source. Production and isolation of this salt, as in the above references, results in some yield loss, thus adding to its cost. The use of acetone or similar solvents as the reaction medium requires downstream equipment for separation of solvent, product and by-products and recycling of solvent to the main processing stages. The use of acetone also requires great care in downstream product recovery steps such as washing, to prevent formation of emulsions.
It would be advantageous to provide a process for the production of S-tricyclohexyltin-O,O-diisopropyl dithiophosphate in which it would not be necessary to utilize potassium diisopropyl dithiophosphate per se.
It would also be advantageous to provide a process for the production of S-tricyclohexyltin-O,O-diisopropyl dithiophosphate in which a solvent would not be necessary, as the cost of a solvent and of solvent recovery and recycling equipment could be saved. Additionally, if a solvent could be omitted from the process, the capacity of apparatus for the reaction could be improved, or smaller and therefore less expensive apparatus could be utilized for the same production capacity.
It would be advantageous to provide a process for production of maximum yields of S-tricyclohexyltin-O,O-diisopropyl dithiophosphate based on the intermediate tricyclohexyltin chloride.
The invention described herein, in its various embodiments, achieves some or all of the advantages stated above as well as other advantages which will be apparent from the description which follows.